Process for the preparation of 2-bromo 3-halo propene-1



United States Patent 3,197,514 PROCESS FOR THE PREPARATION OF Z-BROMO 3-HALO PROPENE-l Hendricus Gerardus Peer, Riiswijk, South Holland, Netherlands, assignor to The Nederlandse Organisatie voor 3,1915 14 Patented July 27, .1965

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bromine content 77.7%; identification by means of infrared analysis shows that the substance is indeed 2,3-dibromo propene-l.

In this case no other substances and especially no b the r action mix- Toegepast-Natuur-Wetenschappelijk Onderzoek ten 5 tetra broino Propane can 6 found m e n ture nor in the final product. Behoeve van Nr verheid, Handel en Verkeer, The Th t f 1 cial C acid and 23 dibmmo Hague, Netherlands, a corporationof the Netherlands 6 mm me 0 a a e i No Drawing. Filed Man 16 1961, sen 95,102 propene-l formed in the reaction can be separated by Claims priority, application Great Britain, Mar. 28, 1960, fractional (l1S-t11lat10n.- Y p v 10,897/ 60, 10,898/ 60; May 20, 1960, 17,889/60 10 In other inert solvents tetrabromo propane The portion of the term of the patent subsequent to H B h i g 22 gggiz g may also be formed by the reaction between bromine and allene, although under specific conditions the process Th 1s mvemlon relates to a PrimesS for the Pl'eparatlon 0f leads to the formation of substantially only 2,3-dibromo 2,3-d1bromo propene-l and of 2-bromo S-chloro propenepr0pens 1 .1; inthe specification and claims these products are EXAMPLE 2 covered by the term Z-brorno 3-halo propene-l. A1

lene is dissolved 1n 75 ml. of CHCll 'bromme dlS- b l g 2 ii' f ifff solved in 125 ml. of cncl is added in the dark over 6 0 mm m a g 0 yle y N a e e a period :of 3%. hours while stirring, stirring is continued (CHFkCHQ for an hour, the reaction mixture is shaken with ad with either bromine or a mixture of bromine and chlorine aqueous solution of NaI-ICO (5%), then with water and in the presence of an inert solvent. If bromine is used finally dried over anhydrous Na SO the chloroform is 2,3-dibromo propene-l (CHFCBrCH Br) is formed. removed by distillation and the residue is fractionated. If a mixture of bromine and chlorine is used 2-bromo 3- r The results are recorded in Table I. In the first, second chloro propene-l (CI-l =CBrCH Cl) is formed. and fifth experiments'the temperature is minus 17 C.;

The term inert solvent as used herein means a 801- in the third experiment it is 20 C.; in the fourth experivent which, under the reaction conditions, does not apment it is C. This table shows that it is possible to preciably react either with the reactants or with the reobtain dibromo propene-l as the main or even sole reaction products; examples of such solvents are chloroaction product. The dibromo compound is denoted by form and carbon tetrachloride. 30 di-BP;the tetrabromo propane by tetra-BP.

T able I Bromine Molar Fraction No. Yield percent Molar C3114 added in ratio ratio in ml. grams Bl'ztC3H4 di-BP:

di-BP tetraBP dl-BP tetra-BF tetra-BF 12 0.5 4 4 71 69 Nil 100=0 21. 3 1. 0 5 5-4 05 Nil 100:0 24.8 1.0 6 65-1; 61 4 97:3 17. 4 1. 0 7 7-1; 65 nil 10010 48. 3 2. 0 s S-a 2s 2s 50 I The Z-bromo 3-halo propene-l as defined herein before Fraction No. 4 is 10.4 g. boiling at 68 to 72 C. at is a valuable compound for instance as a nematocide. mm. Hg;

When working in a dilute system in glacial acetic acid, 45 Fraction No. 4-a i nil g the reaction of allene with bromine takes place at one of Fraction No. 5 is 17.1 g. boiling at 68 to 70 C. at the two double bonds of the allene only, the resulting 60 mm. Hg; product being 2,3-dibromo propene-l. Fraction No. S-ais nil g.;

EXAMPLE 1. Fraction No. 6 is 18.9 g. boiling at 68 to 72 C. at Into a solution of 4 cc. of bromine in 800 cc. of glacial 50 Q o acetic acid at room temperature, allene (CH =C=CH g g 'bolhng at 123 w 140 at is introduced at a rate of 20 cc. per minute until the solu- 7 14 1 b 6 0 tion becomes colourless. The introduction of aliens is 60 lac 1s 01mg at 7 to 69 at then stopped and nitrogen is passed through the reaction 5 mixture in order to remove a possible excess of allene. 5 faction D The reaction mixture is then poured out into 1600 cc. of Fracnon 8 1s 8 bolhng at 68 lo 72 at 60 ice water, 600 cc. of ether is added and, while cooling with g I 0 ice the mixture is neutralised with aqueous NaOH Fraction No. 8-a is 14.5 g. boiling at 123 to 133 C. at (20%). The ethereal layer is separated, dried over I anhydmus Sodium l h d f ti t d 60 It instead of chloroform carbon tetrachloride 1s used The yield of 2,3-dibmmo propane-1 i b t fr 60 under the same conditions as in Example 2, similar reto calculated on the amount of bromine originally sults are obtained; vide Table II. In all cases the tempresent; boiling point at 60 mm. Hg from 67 to 70 C.; peraturc is 17 C.

' Table II Bromine Molar Fraction No. Yield percent Molar I 03H. added in ratio ratio in moles moles Bra: CaHs di-BP:

dl-BP tetra-BF di-BP tetra-B]? tetra-BF 0.15 0.075 0.5 9 9-0 77 Nil 100:0 0.15 0.15 1.0 10 10-a 47 9 :15 0.10 0.20 2.0 11 11-4 47.0 17 74:26

i i. i a

In the first two experiments the yield is calculated on the total of bromine added; in the last experiment on C3H4.

, Fraction No. 9 is 11.8 g. boiling at 68 to 69 C. at 60 mm. Hg;

Fraction No. 9-11 is nil g.;

Fraction No. 10 is 14.5 g. boiling at 68 C. at 6 mm. Hg;

Fraction No. 10-11 is 5.0 g. boiling at 124 to 128 C. at- 17 mm. Hg;

Fraction No. 11 is 10 g. boiling at 68 to 70 C. at .60 mm; Hg;

Fraction No. l1-a is 7.3 g. boiling at 126 to 140 C. at 17 mm. Hg.

EXAMPLE I 3 19.5 grams of bromine (0.12 mole) are introduced into a solution of 8.7 grams of chlorine (0.12 mole) in 243 grams of carbon tetrachloride. This solution is then slowly added dropwise in the dark and with a nitrogen atmosphere to a solution of 5470 ml. (0.245 mole) of allene in 350 grams of carbon tetrachloride at minus 30 C. The mixture is kept at this temperature for one hour and for a further two hours at +20 .0. After this the reaction mixture is shaken with an aqueous solution of sodium bicarbonate (5% then with water and is finally dried over anhydrous Na SO The solvent is removed by distillation and further distillatidn gives four fractions, vide Table III.

Table III Fraction Weight Boiling point 11 in grams in O.

0. 4 65-92 1. 4739 2.6 -92-l13 1. 4951 p v 14. 4 113-114 1. 4992 7. 4 38-99/11 mm. Hg

The third fraction consists substantiallyof 2-bromo 3- chloro propene-l as is shown by chemical analysis, boiling point and infrared spectrography which produce values which are the same as those obtained with a control sample of 2-bromo-3-chloro propene-l.

Fraction 2 probably contains 2,3-dichloro propene. Fraction 4 probably contains tetrahalogenation products.

The yield of 2-bromo 3:Ch101'0 propene-l is 41% calculated on the alleneconsumed. It is possible to improve this yield by decreasing the amount of halogen used with respect to the amount of allene.

The identification of the fractions is by infrared spectrography by determination of the halogen content and by refractive index. A typical fraction consisting of substantially solely. 2,3-dibromo propene-l had a bromine content of 79.1 (theoretically it is 80) and an 21 1.5378. A typical fraction consisting of substantially solely tetrabromo propane had a bromine content of 88.60 (theoretically it is 88.89) and an n :1.6158.

If Example 3 is repeated but instead of carbon tetrachloride as the solvent glacial acetic acid is used, there The reaction scheme is probably as follows. chemical structure of allene is 1 CH2:(2)C:(3)CH2 in which the figures between parentheses denote the numbering of the carbon atoms.

In the presence of bromine a bromination takes place at one of the double bonds, say at the double bond between carbon atoms (2) and (3). This addition of bromine starts with a primary addition of a positive bromine Br -ion:

The

Br (A) The structure (A) may be called a bromonium ion. This structure (A) seeks to be stabilized.

If the solvent is inert and bromine is the sole halogenation agent, said stabilization takes place by incorporti-on of a negative bromine Br-ion:

thus leading to the formation of 2,3-dibromo propene-l. If the solvent is inert and a mixture of bromine and chlorine is used it should be noted-that such a mixture reacts as if it were the compound Br+Cl and consequently said stabilization takes place by incorporation of a negative chlorine Cl-ion:

thus leading to the formation of 2-bromo 3-chloro propene-l. Y Y

The examples show that a solvent such as glacial acetic acid is inert if halogenation is done with bromine. But if halogenation is done with a mixture of bromine and chlorine (i.e. with Br+Cl-) it is not 2-bromo 3-chloro vpropene-l which is formed but 2-bromo 3-acetoxy propene-l; this is accounted for by the fact that negative chlorine Cl-ions are markedly less nucleophilic than acetoxy-ions so that (A) is stabilized as follows:

thus leading to the formation of 2-bromo 3-acetoxy propene-l. In this case glacial acetic acid is not inert.

The fact that by solely using bromine and glacial acid as the solvent no 2-bromo 3-acetoxy propene-l is formed but 2,3-dibromo propene-l proves that the negative bromine Br-ion is more nucleophilic than the acetoxy-ion.

As appears from the examples and the tables the first step of the halogenationis an attack on only one of the 3 two double bonds of allene and in some solvents and under certain conditions the addition of bromine stops at thisstage. In other solvents such as ether there is a secondary addition at the second double bond of allene,

is a very substantial formation of 2-bromo 3-acetoxy' appreciable extent by varying the ratio of bromine to allene.

Examples of the latter type of inert solvents are ether,

benzene, dioxane, ethyl acetate and carbon disulphide. In these solvents with an initial ratio of 1 mol bromine per 1 mol allene and bromination at 20 C. in the dark,

in the final mixture about 3 to 4 moles of 2,3-dibromo propene-l per 1 mol tetrabromo propane are found. By increasing the amount of allene to about 2 mol per mol of bromine the formation of the tetrabromo compound is suppressed in favour of the formation of the dibromo compound. In ether as the solvent and an amount of 2 moles of allene per mol of bromine, bromination in the dark at 0 C. leads to the formation of the'dibromo compound in a molar ratio of about 9 moles .per molof the tetrabromo compound.

But with halogenated hydrocarbons such as carbon tetrachloride, chloroform and methylene chloride (CH CIz), the formation of the dibromo compound is very much more predominant than the formation of the tetrabromo compound even if an excess of bromine is used. In general better results are obtained at lower temperatures of reaction. For instance with methylene chloride as the solvent at -]-2() C. rather much tetrobromo propane is formed.

It is advisable to use a solvent having at a specified pressure a boiling point substantially different from the boiling point of the 2-bromo 3-halo propene-l for in such a case separation of said compound from the solvent can easily be done by fractional distillation.

Separation of the reaction product from a water-miscible inert solvent is also possible by adding to the reaction mixture a substance such as water which precipitates the reaction product. Other methods for such a separation can easily be devised by any one, skilled in the art.

All experiments recorded in the examples and the tables are on a laboratory scale. The yields are calculated on the initial amount of bromine, unless otherwise stated. The yields do not add up to 100 because some bromine gets lost, partly in unidentified products. It stands to reason that the yields may be substantially improved if the process is carried out in a large scale apparatus because then slight losses during the isolating steps have only a slight etfect upon the yield.

What is claimed is:

1. A process for the production of substantially pure 2,3-dibromo-propene-1 which comprises the steps of reacting up to the stoichiometric amount of bromine with a solution of allene in a solvent selected from the group consisting of glacial acetic acid, carbon tetrachloride, chloroform and methylene dichloride and recovering said 2,3-dibromo-propene-1 to the substantial exclusion of tetrabrominated products.

2. The process of claim 1 wherein said bromine is dis solved in said solvent and reacted with said solution of allene in the same solvent.

3. The process of claim 1 wherein said bromine is dissolved in said solvent and allene is added thereto.

4. The process of claim 1 wherein said bromine in gaseous form is passed into said solution of allene in said solvent.

References Cited by the Examiner UNITED STATES PATENTS 2,973,393 2/61 Monroe 260654 3,009,967 11/61 Monroe 260654 3,110,740 11/ 63 Peer 260654 OTHER REFERENCES Lespieau et al.: Bull. Soc. Chem. (France), v01. 45, part2, p. 632 (1929).

LEON ZIT'VER, Primary Examiner. ALPHONSO D. SULLIVAN, Examiner. 

1. A PROCESS FOR THE PRODUCTION OF SUBSTANTIALLY PURE 2,3-DIBROMO-PROPENE-1 WHICH COMPRISES THE STEPS OF REACTING UP TO THE STOICHIOMETRIC AMOUNT OF BROMINE WITH A SOLUTION OF ALLENE IN A SOLVENT SELECTED FROM THE GROUP CONSISTING OF GLACIAL ACETIC ACID, CARBON TETRACHLORIDE, CHLOROFORM AND METHYLENE DICHLORIDE AND RECOVERING SAID 2,3-DIBROMO-PROPENE-1 TO THE SUBSTANTIAL EXCLUSION OF TETRABROMINATED PRODUCTS. 